Method of making slip ring-commutator devices



April 16, 1963 e. P. BENTLEY ETAL 3,085,951

METHOD OF MAKING SLIP RING-LCOMMUTATOR DEVICES Original Filed June 11,1957 2 Sheets-Sheet 1 Fig.1

INVENTORS GEORGE P. BENTLEY GEORGE C. McNABB EDWARD L. LEWIS Fig-4 April16, 1963 G. P. BENTLEY ETAL METHOD OF MAKING SLIP RING-COMMUTATORDEVICES 2 Sheets-Sheet 2 Original Filed June 11, 1957 Fig.7

INVENTORS: GEORGE P. BENTLEY GEORGE C.MCNABB EDWARD L. LEWIS THEIRATTORNEYS States nite The invention in this application, which is adivision of application Serial No. 665, 021, now Patent 2,918,542,relates to a method of making slip ring-commutator devices.

An object of the invention is to provide a method of making compact andrugged commutating devices particularly suited for use in high speedrotary switching devices.

Another object of the invention is in the provision of a method ofmaking integrated slip ring-commutator assembles which permits ofdivision of commutator segments with dividing head accuracy.

Another object of the invention is in the provision of a method ofmaking integrated slip ring-commutator assembles having long electricalleakage paths between commutator segments.

Another object of the invention is in the provision of a method ofmaking slip ring commutator devices having in line cylindricalcommutating surfaces whereby phase errors due to brush width variationsare eliminated.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings in which like referencenumerals designate like parts throughout the figures thereof andwherein:

FIGURE 1 is a plan view of an assembled slip ringcommutator device;

FIGURE 2 is a top view of an assembled slip ringcornmuntator device;

FIGURE 3 is a fragmentary perspective view of a commutator ring beforeseparation of the segments;

FIGURE 4 is a cross sectional view taken along lines 44 of FIGURE 1;

FIGURE 5 is a view in section through the commutator assembly prior tomachining to separate the cornmutator segments;

FIGURE 6 is a view in section through the commutator following machiningto separate the commutator segments and expose the inserts to enablethem to be removed by electrolytic etching;

FIGURE 7 is a view in section taken through one side of the slip ring;and

FIGURE 8 is a view in section taken through one side of the outerretaining ring of the commutator slip ring device.

Referring now to the drawings wherein like reference charactersdesignate like or corresponding parts throughout the several views, andparticularly to FIGURES 3, 4, 7 and 8, the slip ring-commutatorconstruction comprises a slip ring 12, a commutator ring 13, and anouter retaining ring 14. The slip ring comprises an annular body portion15 having annular flanges 16 and 17 extending axially from diametricallyopposite sides of the body portion flush with the top and bottomsurfaces of the body portion. Flange 16 is relatively thinner thanflange 17 and is radially slotted about its periphery.

The commutator ring 13 preferably formed of rhodium comprises as mostclearly seen in FIGURE 3 an annular 3,fl85,951 Patented Apr. 16., 1963body portion 18 having first and second annular flanges 19 and 20extending axially from opposite sides of the body portion flush with thebottom surface thereof, and third and fourth annular flanges 22 and 23extending axially from opposite sides of the body portion flush with thetop surface thereof. As seen in FIGURE 3 the third flange 22 is longerthan the fourth flange 23. Both the third and fourth flanges are furtherprovided at their ends with radially extending annular flanges 24 and 25thereby forming an annular channel in the outer surface of thecommutator ring. The commutator ring is thereafter provided with equallyspaced stepped radial slots 27 (FIG- URES 1 and 3) about its peripheryfrom the channelled top surface down into the first and second flanges,the number of slots depending on the number of segments desired for aparticular application. It is to be noted that the radial distances tothe inner peripheries of both the slip ring and commutator ring areequivalent.

The outer retaining ring 14 (FIGURE 8) comprises an annular body portion28 which has an axially extending flange 29 extending from one sideflush with the bottom thereof, and a relatively long axially extendingflange 30 extending from the same side as flange 29 and flush with thetop surface thereof. As seen in FIGURE 1, which illustrates as specificembodiment, the upper flange 30 is provided with equally peripherallyspaced axially extending grooves 32, one of which has a substantiallycutout portion 33, and with a plurality of similar relatively narrowindexing or alignment reference grooves 34. Additionally the bodyportion 28 is provided with a plurality of holes 35 about its circularface which in combination with a potting compound provides strength andrigidity to the assembled wafer.

In assembly the slip ring 12 is placed adjacent the commutator ring 13with the flange 16 thereof overlapping the first flange 19 of thecommutator ring and maintained spaced therefrom by .a separator ring 36(FIGURE 5) formed of an electrochemically active metal such as aluminum.Electrochemically active keys 37 are also placed within the narrowportion of each of the stepped radial slots 27 for reasons Which willhereinafter appear. Insulated lead wires 38 are secured as by solderingto predetermined ones of the segments 39 formed by said slots in thecommutator ring and a lead wire 46* to the slip ring. The lead wires 38and 40 are then caused to lie flat in the annular channel 26 in theouter surface of the commutator ring. The outer retainer ring 14 is thenplaced with its long flange 30 over both the slip ring and commutatorring and with its flange 29 between the second and fourth flanges 26 and23 of the commutator ring; the lead wires being brought out through thecutaway groove 33 (FIGURES 2 and 5). The rings disposed with respect toeach other as described above are held in a suitable jig and a plottingcompound 42 of insulating material such as an epoxy resin whosecoeflicient of thermal expansion matches that of the metal parts ispoured into and fills all the slots in and spaces around and between theintermeshing flanges of the rings and the wide portion of the steppedslots 27 between segments whereby the assembly becomes an integratedannular wafer of great strength and rigidity. The resulting wafer isdisclosed in FIGURE 5.

Thereafter the wafer is placed on a lathe and the inner surfaces of theslip ring and commutator ring (shown dotted in FIGURE 4) are turned downuntil the bottom of the radial slots 27 (FIGURE 3), which extend downinto the lower flanged body portion of the commutator ring are reached(line 43) thereby dividing the commutator ring into individual segmentsinsulated from one another and exposing inner edges of the keys 37 asshown in FIGURE 6. Thereafter the remainder of aluminum insert 35separating the slip ring and commutator ring and the keys 37 within thenarrow portion of the stepped radial slots 27 are electrochemicallyetched away to provide undercut segments as shown in FIGURE 4. As isapparent, the contact surfaces of the segments are cylindrical sectionsthereby permitting accurate timing.

The above method permits division of the commutator segments 39 from oneanother with dividing head accuracy as they are an integral part of theretaining ring 14 during embedment. The above method which is termeddouble slotting" provides a commutator having long electrical leakagepaths between segments with concomitant high intersegment resistances.The leads 38 which as heretofore stated are brought out through onegrooved section of the retaining ring flange as shown in FIGURE 2 areadapted when the ring or rings are assembled within a cylindrical casingto lie within the groove 32 thereof as seen in the assembled view ofFIGURES l and 2.

It should be understood, that the foregoing disclosure relates to only apreferred embodiment of the invention and that it is intended to coverall changes and modifications of the example of the invention hereinchosen for the purposes of the disclosure, which do not constitutedepartures from the spirit and scope of the invention.

The invention claimed is:

1. The method of making annulated wafer like commutators having firstand second rings of equivalent internal diameters, said first ringhaving an annular body portion, first and second flanges extendingaxially from diametrically opposite sides of and flush with the radiallyouter and radially inner surfaces thereof, said second ring having abody portion, first and second flanges extending axially from oppositesides of and flush with the radially inner surface thereof, third andfourth flanges extending axially from opposite sides of and flush withthe radially outer surface thereof and fifth and sixth flanges extendingradially from and flush with the ends of said third and fourth flanges,said method comprising the steps of, forming slots in said second ring,said slots extending inwardly from the radially outer surface of saidsecond ring and having inner ends spaced from the radially inner surfaceof said second ring, inserting electrochemically active metal keys insaid slots adjacent to said inner ends, placing said first and secondrings adjacent one another with said second flange of the first ringoverlying and spaced from said first flange of said second ring, fillingthe spaces between said intermeshing rings with an insulating pottingmaterial, radially boring said radially inner surface of said secondring through to the slots thereby dividing said second ring into aplurality of radial segments and exposing said keys therebetween, andthereafter electrochemically etching away said keys to provide separate,undercut segments.

2. The method of making slip ring-commutator wafers having a slip ringand a commutator ring of equivalent internal diameter, said rings havingirregular cross sections, said method comprising the steps of formingsubstantially radially extending slots in said commutator ring extendinginwardly from its outer periphery, said slots having inner ends spacedoutwardly from the inner periphery of said commutator ring to form aplurality of segments joined together by an inner peripheral annularweb, inserting electrochemically active metal keys in said inner ends ofsaid slots, placing said rings adjacent one another with their crosssections spaced from and overlapping each other, filling said spacesbetween said rings and segments with a potting compound to secure saidrings and segments together and electrically insulate them from oneanother, cutting away said web to separate said segments from each otherand expose said keys and thereafter etching away said keys to provideundercut segments.

3. The method of making commutators comprising the steps of cuttingstepped radial slots in the outer periphery of a cylindrical ring, saidslots having inner ends spaced from the inner periphery of said ring,inserting electrochemically active metal keys in said inner ends of saidslots, filling the remainder of said slots with a bonding insulatingmaterial, boring out the internal surface of said slotted ring to exposesaid inner ends of said slots and said keys therein to separate saidring into segments, and thereafter electrochemically etching away saidkeys to provide undercut segments.

4. A method of making commutators comprising forming stepped slots ofprogressively narrower width extending from one side of a metalliccommutator ring toward an opposite side thereof, said slots havingclosed ends spaced substantially equal distances from said opposite sideof said ring, inserting keys in said slots adjacent to the closed endsthereof, the remaining portions of said slots being open, filling theopen portions of said slots with, and at least partially embedding saidring in, a bonding insulating material, cutting away said ring from saidopposite side to said closed ends of said slots to divide said ring intoa plurality of separate segments and expose a portion of each keytherebweteen, and thereafter removing said keys from between saidsegments.

References Cited in the file of this patent UNITED STATES PATENTS1,195,861 Smith Aug. 22, 1916 1,624,597 Heathcote Apr. 12, 19271,845,115 Apple Feb. 16, 1932 2,156,156 Mahlck Apr. 25, 1939 2,936,519Blackman May 17, 1960

1. THE METHOD OF MAKING ANNULATED WAFER LIKE COMMUTATORS HAVING FIRST AND SECOND RINGS OF EQUIVALENT INTERNAL DIAMETERS, SAID FIRST RING HAVING AN ANNULAR BODY PORTION, FIRST AND SECOND FLANGES, EXTENDING AXIALLY FROM DIAMETRICALLY OPPOSITE SIDES OF AND FLUSH WITH THE RADIALLY OUTER AND RADIALLY INNER SURFACES THEREOF, SAID SECOND RING HAVING A BODY PORTION, FIRST AND SECOND FLANGES EXTENDING AXIALLY FROM OPPOSITE SIDES OF AND FLUSH WITH THE RADIALLY INNER SURFACE THEREOF, THIRD AND FOURTH FLANGES EXTENDING AXIALLY FROM OPPOSITE SIDES OF FLUSH WITH THE RADIALLY OUTER SURFACE THEREOF AND FIFTH AND SIXTH FLANGES EXTENDING RADIALLY FROM AND FLUSH WITH THE ENDS OF SAID THIRD AD FOURTH FLANGES, SAID METHOD COMPRISING THE STEPS OF, FORMING SLOTS IN SAID SECOND RING, SAID SLOTS EXTENDING INWARDLY FROM THE RADIALLY OUTER SURFACE OF SAID SECOND RING AND HAVING INNER ENDS SPACED FROM THE RADIALLY INNER SURFACE OF SAID SECOND RING, INSERTING ELECTROCHEMICALLY ACTIVE METAL KEYS IN SAID SLOTS ADJACENT TO SAID INNER ENDS, PLACING SAID FIRST AND SECOND RINGS ADJACENT ONE ANOTHER WITH SAID SECOND FLANGE OF THE FIRST RING OVERLYING AND SPACED FROM SAID FIRST FLANGE OF SAID SECOND RING, FILLING THE SPACES BETWEEN SAID INTERMESHING RINGS WITH AN INSULATING POTTING MATERIAL, RADIALLY BORING SAID RADIALLY INNER SURFACES OF SAID SECOND RING THROUGH TO THE SLOTS THEREBY DIVIDING SAID SECOND RING INTO A PLURALITY OF RADIAL SEGMENTS AND EXPOSING SAID KEYS THEREBETWEEN AND THEREAFTER ELECTROCHEMICALLY ETCHING AWAY SAID KEYS TO PROVIDE SEPARATE, UNDERCUT SEGMENTS. 